1. Field of the Invention
This invention pertains to a novel pharmaceutical dosage component exhibiting a controlled rate of release of a bronchodilator agent of the .beta.-adrenergic agonist type.
2. Prior Art
The technique of microencapsulation of pharmaceutical substances is generally known [Phares and Sperandio, J. Pharm. Sci. 53, 515-518 (1964) and Luzzi, J. Pharm. Sci. 59, 1367-1376 (1970)].
Microencapsulation of a number of pharmaceuticals with ethylcellulose by organic phase separation is also known and is described in Miller and Anderson U.S. Pat. No. 3,155,590, Anderson et al. U.S. Pat. No. 3,341,416, and Powell and Anderson U.S. Pat. No. 3,576,759, issued Nov. 3, 1964, Sept. 12, 1967 and Apr. 27, 1971, respectively, and in Holliday et al. U.S. Pat. Nos. 3,488,418 and 3,524,910, issued Jan. 6 and Aug. 18, 1970, respectively.
Bronchodilator agents of the .beta.-adrenergic agonist type constitute a well-known class of pharmaceutical compounds (AMA Drug Evaluation, 3rd Edition, Publishing Sciences Group Inc., Littleton, Mass., 1977, pgs. 631-636 and W. C. Cutting, Cutting's Handbook of Pharmacology, 5th Edition, Meridan Corp., New York, 1972, pgs. 424-435). These compounds usually affect the adrenergic receptors of both the lungs (.beta.-2) and the heart (.beta.-1), thus producing bronchial relaxation (bronchodilation) accompanied by cardiac stimulation (tachycardia). Published reports show that much effort has been expended in attempting to separate the .beta.-1 and .beta.-2 effects of .beta.-adrenergic agents with only partial success and accordingly, research directed at divorcing the cardiac effects from the bronchial effects continues.